[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Lower urinary tract and male genital system](https://durgical.com/en/general-pathology/areas/urinary-male/) › Urothelial tumours: morphology, grade and stage

# Urothelial tumours: morphology, grade and stage

- Lesion

Grade and depth of invasion decide prognosis: from benign papillomas to carcinoma invading the bladder muscle.

Updated Nov 12, 2026

## Key points

- Papilloma: delicate papillae lined by normal-looking urothelium; inverted papilloma grows into the stroma and is benign.
- PUNLMP and low-grade carcinoma: orderly cells, recur often, rarely progress.
- High-grade papillary carcinoma: disordered, pleomorphic cells, frequent invasion.
- Carcinoma in situ: flat, full-thickness or patchy high-grade atypia; cells shed into urine (positive cytology).
- Invasion of the muscularis propria (detrusor) is the decisive step for treatment; the muscularis mucosae must not be confused with it.

## What it is

Noninvasive urothelial tumours are papillary or flat. Papillary lesions range from papilloma (rare, benign) and papillary urothelial neoplasm of low malignant potential (PUNLMP) to low-grade and high-grade papillary carcinoma. Flat lesions range from dysplasia to carcinoma in situ, a high-grade lesion that is often multifocal. Once invasive, staging depends on depth: lamina propria (T1), muscularis propria (T2), perivesical fat (T3) and adjacent organs (T4). The renal pelvis and ureter host the same tumours and can obstruct the kidney.

## Structure

- Gross: papillary, cauliflower-like tumours, or flat red velvety patches in carcinoma in situ; large tumours ulcerate.
- Most arise on the lateral or posterior walls and the trigone.
- Variants of invasive carcinoma include squamous and glandular differentiation, micropapillary, nested and plasmacytoid forms, which are more aggressive.
- Upper-tract tumours are papillary masses in the pelvis or ureter, often with hydronephrosis.

## Noninvasive urothelial lesions

| Lesion | Architecture | Cytology | Risk |
| --- | --- | --- | --- |
| Papilloma | Fine papillae | Normal urothelium | Very low |
| PUNLMP | Papillae, thickened urothelium | Minimal atypia | Recurs; progression rare |
| Low-grade papillary carcinoma | Papillae, mostly orderly | Mild variation in nuclei | Frequent recurrence; invasion uncommon |
| High-grade papillary carcinoma | Papillae, disordered | Marked pleomorphism, mitoses | Invasion and metastasis common |
| Carcinoma in situ | Flat | High-grade cells, loss of cohesion | High risk of invasion |

## Clinical notes

- Cystoscopy and urine cytology are used for diagnosis and long follow-up because of recurrences.
- Tumours that invade muscle need cystectomy or combined therapy; noninvasive tumours are resected and treated with intravesical therapy such as BCG.

## Memory aid

Papillary or flat, low or high, above or into the muscle: the three questions in every bladder biopsy.

## Test yourself

Think of the answer, then tap the question to see it.

## Which layer must be invaded to stage a bladder tumour as T2?

The muscularis propria (detrusor muscle).

## Why is urine cytology useful in carcinoma in situ?

Its high-grade cells are poorly cohesive and shed into the urine.

## How do low-grade papillary carcinomas usually behave?

They recur frequently but seldom invade.

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## Elsewhere in DurgiPedia

- [Ureter, bladder and urethra: urothelium](https://durgical.com/en/histology/ureter-bladder-and-urethra-urothelium/)
- [Dysplasia and carcinoma in situ](https://durgical.com/en/general-pathology/dysplasia-and-carcinoma-in-situ/)
- [Grading and staging: what TNM means](https://durgical.com/en/general-pathology/grading-and-staging-what-tnm-means/)

## Connections

## Related 4

- [Urothelial carcinoma: pathogenesis](https://durgical.com/en/general-pathology/urothelial-carcinoma-pathogenesis/)
- [Other bladder tumours](https://durgical.com/en/general-pathology/other-bladder-tumours/)
- [Dysplasia and carcinoma in situ](https://durgical.com/en/general-pathology/dysplasia-and-carcinoma-in-situ/)
- [Grading and staging: what TNM means](https://durgical.com/en/general-pathology/grading-and-staging-what-tnm-means/)

## Related conditions 2

- [Bladder cancer](https://durgical.com/en/conditions/bladder-cancer/)
- [Lynch syndrome (hereditary non-polyposis colorectal cancer)](https://durgical.com/en/conditions/lynch-syndrome/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Bladder Cancer](https://www.ncbi.nlm.nih.gov/books/NBK536923/) (StatPearls (NCBI Bookshelf), 2024).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/urothelial-tumours-morphology-grade-and-stage/